Organic Light Emitting Diode Display Having Photodiodes

ABSTRACT

Systems, methods, and devices are provided in which photodetectors disposed throughout a display are used to control the display brightness. The photodetectors are to be used for ambient light sensing, proximity sensing, or to compensate for aging OLEDs. In some embodiments, photodiodes are fabricated with OLEDs during the TFT fabrication process. In some embodiments, the photodetectors may be disposed throughout the display in zones containing OLEDs. The photodetectors are used to control the display brightness and color for the OLEDs in areas around each photodetector based on ambient light, aging, and/or nearby objects. A controller makes driving strength adjustments to the OLEDs in each zone independent of other zones. Photodetectors disposed throughout the display may improve proximity sensing and provide additional functionality to the device.

This application is a continuation of U.S. patent application Ser. No.13,364,100, filed Feb. 1, 2012, which is hereby incorporated byreference herein in its entirety. This application claims the benefit ofand claims priority to U.S. patent application Ser. No. 13,364,100,filed Feb. 1, 2012.

BACKGROUND

The present disclosure relates generally to electronic displays and moreparticularly, to photodetectors in a display.

This section is intended to introduce the reader to various aspects ofart that may, be related to various aspects of the present disclosure,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader weith background information tofacilitate a better understanding of the various aspects of the presentdisclosure. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

Electronic devices and systems increasingly include display screens aspart of the user interface of the device or system. As may beappreciated, display screens may be employed in a vide array of devicesand systems including desktop computer systems, notebook computer, andhandheld computing devices; well as various consumer products, such ascellular phones, televisions, and portable media players.

To display images, videos, and user interfaces, displays use arrays ofpixels, each pixel having multiple colors. Primary colors of light(e.g., red, green, and blue) may be combined in each pixel to createmany other colors, including white. Controllers drive pixels withcoordinated instructions to create an image on the display. Somedisplays involve illuminating a backlight through a light-modulatingliquid crystal layer (e.g., typical liquid crystal displays) whileothers involve directly illuminating each pixel to a desired intensity(e.g., organic light emitting diode (OLED) displays).

Because each OLED may emit its own colored light, OLED displays may bethinner and lighter than displays requiring a backlight. OLEDs may alsobe desirable because they may be fabricated on flexible or rigidsubstrates. OLED displays may also allow better viewing angles andbetter color than some liquid crystal displays (LCDs).

However, displays do not always operate in the same lightingenvironments. The perception of emitted light from a display may beaffected by lighting conditions. Changing the brightness of a displaycan improve the perceived image of the display. For example, a dimdisplay may provide sufficient visibility in dark environments, while abright display may provide better visibility in a bright environment.However, controlling the brightness of a display to improve displayvisibility may not always be as straightforward as changing thebrightness of the entire display according to a single measurement ofthe environmental light. For example, the ambient light on a display maynot be uniform across the display, and displays are frequently movedsuch that their surrounding environment is dynamic.

Furthermore, the appearance of OLED displays may not remain constantindefinitely. As OLED displays age through use, their brightness and/orcolor may change. Some OLEDs, particularly blue OLEDs, age more quicklythan others, which may change the appearance of the display. Over timeas the OLEDs age, images shown on parts of the display may appear muchdifferent from the intended image. OLED controllers may make changes tocompensate for such shifts in brightness and color. However, aging mayoccur differently across a display. For example, aging may occur in anunpredictable manner due to the manner in which end users use thedevice.

Further, OLED displays may be used on many mobile devices, includingcellular phones and such OLED displays may also be touch-sensitive.Presently, it is desirable to utilize a proximity sensor to turn off thedisplay when a user places the phone near the user's face. This bothsaves power and prevents undesired inputs to the touch screen. However,such proximity sensors are typically placed outside of the display area,thus creating some inaccuracies when turning the display on and off.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. Itshould be understood that these aspects are presented merely to providethe reader with a brief summary of these certain embodiments and thatthese aspects are not intended to limit the scope of this disclosure.Indeed, this disclosure may encompass a variety of aspects that may notbe set forth below.

Embodiments of the present disclosure relate to OLED displays andmethods to adjust OLED displays to maintain a desired appearance.Photodetectors may be disposed in the OLED display with individual OLEDsor zones of OLEDs to adjust their emitted light. In an embodiment, eachphotodetector may detect light incident to the display. Such detectedlight may be from OLEDs of the display, from the ambient light, or both.Ambient light may affect how the light emitted from the display isperceived. For example, a corner portion of the display may be in ashadow while the remainder is under a bright light. If all the OLEDs areset to the same brightness and/or color level, either the shaded corneror the remainder of the display may be less visible than the other. Thephotodetectors may enable controllers to brighten or dim the entiredisplay and/or compensate each OLED or group of OLEDs (e.g., OLEDs inthe corner portion) to improve the appearance of the display as a whole.This may improve the versatility of the display in different operatingenvironments.

In other embodiments, each OLED may be adjacent to a photodetector tomeasure the aging characteristics of that particular OLED. Aged OLEDsmay emit light different from less aged OLEDs, which may result in apoor display quality for unevenly aged displays. For example, if all theblue OLEDs in a region of the display have aged more than the red andgreen OLEDs, that region of the display may appear dimmer and/or moreyellow than desired. As portions of the display age at different rates,the quality of a displayed image may decrease. By adjusting the drivingstrength of each OLED, controllers may compensate individual OLEDs forshifts in brightness and/or color based on the photodetectormeasurements of each OLEDs aging. Compensations to driving strength maycause an OLED to emit brighter light and/or light of a differentwavelength than before the compensation. This adjusted OLED may now emitlight at a desired brightness and/or color. This may prolong the usefullife of a display and maintain a desirable display appearance for longerthan would otherwise be possible.

In other embodiments, multiple photodetectors may be disposed in an OLEDdisplay to sense the proximity of nearby objects, including a user'sfinger or face. Photodetectors may be disposed with OLEDs or zones ofOLEDs across the display, as mentioned above, or in a peripheral area ofthe display to control when the OLED display is to be turned off. In anembodiment, when the photodetectors sense the user's face near thedisplay, the display may be turned off.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawings inwhich:

FIG. 1 is a block diagram of an electronic device with an electronicdisplay and its components, in accordance with aspects of the presentdisclosure;

FIG. 2 is a perspective view of an example of the electronic device ofFIG. 1 in the form of a computer, in accordance with aspects of thepresent disclosure;

FIG. 3 is a front view of an example of the electronic device of FIG. 1in the form of a handheld device, in accordance with aspects of thepresent disclosure;

FIG. 4 is a cross-sectional side view of a portion of an OLED having asensor disposed over an OLED device, in accordance with aspects of thepresent disclosure;

FIG. 5 is a cross-sectional side view of a portion of an OLED having asensor in the OLED layer, in accordance with aspects of the presentdisclosure;

FIG. 6 is a cross-sectional side view of a portion of an OLED having asensor disposed beneath an OLED device, in accordance with aspects ofthe present disclosure;

FIG. 7 is a front view of an OLED array with a respective photodetectordisposed with each OLED, in accordance with aspects of the presentdisclosure;

FIG. 8 is a flowchart depicting a method for operating an OLED displayto compensate for aging OLEDs, in accordance with aspects of the presentdisclosure;

FIG. 9 is a front view of zones across the display of a handheld device,in accordance with aspects of the present disclosure;

FIG. 10 is a front view of an OLED array arranged in zones with aphotodetector disposed in each zone, in accordance with aspects of thepresent disclosure;

FIG. 11 is a flowchart depicting a method for operating an OLED displayto compensate for ambient light, in accordance with aspects of thepresent disclosure;

FIG. 12 is a front view of photodetectors disposed on the periphery ofthe display of a handheld device, in accordance with aspects of thepresent disclosure; and

FIG. 13 is a flowchart depicting a method for operating an OLED displayto detect objects near the display and alter the display in response, inaccordance with aspects of the present disclosure.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments will be described, below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be appreciated that in the development of any such actualimplementation, as in an engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features.

The present disclosure is directed to systems, displays, and techniquesintegrating photodetectors with an electronic display to improve theappearance and/or functionality of the display OLED displays use anarray of OLEDs to show an image across the display. Each OLED emitslight of a certain color and brightness based on its driving conditionsand internal components. Ambient light may affect the perception andappearance of the color and/or brightness of the light chatted by thedisplay. Photodetectors disposed within an OLED display may detectambient light on different parts of the display so that OLED controllersmay make compensations to the driving conditions of part or all of thedisplay. Sufficient compensation results in a display with a uniformappearance regardless of differences in ambient light across thedisplay.

Also, the color and brightness of an OLED are not constant over timeunder the same driving conditions. As an OLED ages, the color and/orbrightness of its emitted light changes. Photodetectors disposed withinan OLED display may detect these changes so that OLED controllers maymake compensations to the driving conditions to counter the effects ofaging. In some embodiments, photodetectors tare disposed its the displaywith each OLED such that each OLED may be compensated according to itsunique aging characteristics. In other embodiments, photodetectors maybe disposed in the display with groups of OLEDs. For example, thedriving strengths may be adjusted by manufacturing settings, user input,and/or transmitted information from sensors such as photodetectors. Insome embodiments, calibration curves may be employed to adjust thedriving strengths of OLEDs or zones, of OLEDs to compensate for ambientlight and/or aging effects.

The photodetectors also may be used to detect objects near the display.A photodetector may transmit information corresponding to a detectedobject to controller. This transmitted information may be used tocontrol the activation setting of the whole display or portions thereof.Furthermore, the transmitted information may be used to provideadditional functionality to a touch screen interface.

A variety of electronic devices may incorporate the OLED displays havingphotodetectors disposed as mentioned above. One example appears in ablock diagram of FIG. 1, which describes an electronic device 10 thatmay include, among other things, one or more processors 22, memory 28,nonvolatile storage 24, a display 14, input structures 16, aninput/output (I/O) controller 20, I/O ports 18, and/or a network device26. The various functional blocks shown in FIG. 1 may include hardware,executable instructions, or a combination of both. In the presentdisclosure, the processor(s) 22 and/or other data processing circuitrymay be generally referred to as “data processing circuitry.” This dataprocessing circuitry may be embodied wholly or in part as software,firmware, hardware, or any combination thereof. Furthermore, the dataprocessing circuitry may be a single, contained processing module or maybe incorporated wholly or partially within any of the other elementswithin the electronic device 10.

As shown in FIG. 1, the processor(s) 22 and/or other data processingcircuitry may be operably coupled with the memory 28 and the nonvolatilestorage 24. In this way, the processor(s) 22 may execute instructions tocarry out various functions of the electronic device 10. Among otherthings, these functions may include generating image data to bedisplayed on the display 14. The programs or instructions executed bythe processor(s) 22 may be stored in any suitable article of manufacturethat includes one or more tangible, computer-readable media at leastcollectively storing the instructions or routines, such as the memory 28and/or the nonvolatile storage 24. The memory 28 and the nonvolatilestorage 24 may represent, for example, random-access memory, read-onlymemory, rewritable flash memory, hard drives, and optical discs.

The depicted electronic device 10 includes a display 14, such as an OLEDdisplay. In accordance with certain embodiments, the display 14 mayinclude or be provided in conjunction with touch sensitive elements.Such a touch-sensitive display may be referred to as a “touch screen”and may also be known as or called a touch-sensitive display system. Forexample, the display 14 may be a MultiTouch™ touch screen device thatcan detect multiple touches at once.

FIG. 1 is merely one example of a particular implementation and isintended to illustrate generally the types of components that may bepresent in an electronic device 10. These components may be found invarious examples of the electronic device 10. By way of example, theelectronic device 10 of FIG. 1 may be embodied as a computer as depictedin FIG. 2, a handheld device as depicted in FIG. 3, a tablet computer(not shown), or similar devices. Such electronic devices as depicted inFIG. 2 may include a model of a MacBook®, a MacBook® Pro, MacBook Air®,iMac®, Mac™ mini, or Mac Pro® available from Apple Inc. of Cupertino,Calif.

As illustrated in FIG. 2, electronic device 10 includes housing, 12 thatsupports and protects interior components, such as processors,circuitry, and controllers, among others, that may be used to generateimages on display 14. Housing 12 also allows access to user inputstructures 16, such as a touch screen, keypad, track pad, and buttonsthat may be used to interact with electronic device 10. For example,uses input structures 16 may be manipulated by a user to operate agraphical user interface (GUI) and/or applications running on electronicdevice 10. In some embodiments, input structures 16 may be manipulatedby a user to control properties of display 14, such as the brightness orcolor. The electronic device 10 also may include various I/O ports 18that allow connection of device 10 to external devices, such as a powersource, printer, network, or other electronic device.

The electronic device 10 may also take the form of a handheld device 30,as generally illustrated in FIG. 3. The handheld device 30 mayrepresent, for example, a portable phone, a media player, a personaldata organizer, a handheld game platform, or any combination of suchdevices. By way of example, the handheld device 30 may be a model of aniPod® or iPhone® available from Apple Inc. of Cupertino, Calif. In otherembodiments, the handheld device 30 may be a tablet-sized embodiment ofthe electronic device 10, which may be, for example, a model of an iPad®available from Apple Inc.

The handheld device 30 may include an enclosure 36 to protect interiorcomponents from physical damage and to shield them from electromagneticinterference. The enclosure 36 may surround the display 14, which maydisplay indicator icons 38. The indicator icons 38 may indicate, amongother things, a cellular signal strength, Bluetooth connection, and/orbattery life. The I/O interfaces 18 may open through the enclosure 36and may include, for example, a proprietary I/O port from Apple Inc. toconnect to external devices. User input structures 16 in combinationwith the display 14, may allow a user to control the handheld device 30.A microphone 32 may obtain a user's voice for various voice-relatedfeatures, and a speaker 34 may enable audio playback and/or certainphone capabilities.

OLED displays may be incorporated in the electronic device 10, such asthe computer or handheld device 30 as described above. Portions ofdifferent embodiments of photo-sensing OLED displays illustrated inFIGS. 4-6 may generally be referred to as displays 14A, 14B, and 14Crespectively. It may be appreciated that the OLED layer 44 may havemultiple components, including an anode and a cathode with one or moreorganic layers disposed between the anode and cathode. Upon applicationof an appropriate voltage to the OLED layer 44, positive and negativecharges combine in the organic layer(s) to emit light. Thecharacteristics of this emitted light depend at least in part n theapplied voltage and properties of the organic layer(s).

As illustrated in FIG. 4, an embodiment of an OLED display 14 mayinclude multiple layers. The OLED layer 44 maybe disposed over asubstrate 46 and a top layer 40 may disposed over the OLED layer 44. Thesubstrate 46 may include glass, plastic, other suitable materials, orcombinations thereof, and may be either a rigid or flexible material.Further, in different embodiments the substrate 46 may be opaque,reflective, translucent, or transparent. The top layer 40 may form anenvironmental barrier to lessen the exposure of the OLED layer 44 toenvironmental elements such as air, oxygen, water, oils, radiation, andother elements with negative effects on the OLED layer 44. In someembodiments, the top layer 40 may also protect the OLED layer 44 fromdirect environmental contact and shock. The top layer 40 may includeglass, plastic, other suitable materials, or combinations thereof, andmay be either a rigid or flexible material.

OLED displays may be categorized as bottom or top emission. In bottomemission OLED displays, the OLEDs emit light toward and through thesubstrate 46. Bottom emission may utilize a transparent orsemi-transparent substrate 46 and bottom electrode so that emitted lightmay pass through both layers. Top emission OLED displays include OLEDsthat emit light opposite the substrate 46. The substrate 46 of a topemission OLED display may be opaque, reflective, translucent, ortransparent.

The OLED display 14 may also include a sensor layer 42. The sensor layer42 may include sensors such as photodetectors, photo diodes, photoresistors, photocells, and combinations thereof. In various embodimentsthe sensors may be disposed in the substrate such that they receivelight from the direction of the substrate or the direction opposite thesubstrate, and combinations thereof. In some embodiments, aphoto-sensing OLED display 14A may include a sensor layer 42 disposedbetween the OLED layer 44 and the top layer 40. The sensor layer 42 maybe substantially transparent in the OLED display 14A, such that lightemitted by the OLED layer 44 may transmit through the sensor layer 42and out of the OLED display 14A. In another embodiment as illustrated inFIG. 5, the sensors and OLEDs may be on the same layer 43 between thesubstrate 46 and the top layer 40. In such an embodiment, thephotodetectors may be fabricated with the OLEDs during the thin filmtransistor (TFT) fabrication process or another fabrication process. Inyet another embodiment as illustrated in FIG. 6, the sensor layer 42 maybe disposed directly over the substrate 46 and beneath both the OLEDlayer 44 and top layer 40. In another embodiment, sensors may bedisposed in multiple layers.

The sensors disposed within layers 42 or 43 of OLED displays 14A, 14Band 14C may be configured to detect aging characteristics or OLEDs,ambient light, nearby objects, or any combination thereof. Sensors thatreceive the light emitted from OLEDs may be configured to detect agingcharacteristics. For example, for an OLED display 14A as shown in FIG.5, sensors disposed above the OLED layer 44 and directed towards topemission OLEDs may be configured to detect aging characteristics of theOLEDs. As another example, sensors directed upward and disposed belowthe DEED layer 44 of bottom emission OLEDs in accordance with FIG. 6 mayalso be configured to detect aging characteristics. Sensors that receiveambient light may be configured to detect ambient light properties andnearby objects. For example, sensors directed toward the top layer 40and disposed above the OLED layer 44 of top emission OLEDs may beconfigured to detect ambient light and/or nearby objects.

Additional details of the display 14 may be better understood throughreference to FIG. 7, which is a schematic of an OLED array. A display 14may have an array of OLEDs 66, photodetectors 55, a power driver 64 a,an image driver 64 b, a controller 62, and possibly other components.The OLEDs 66 are driven by the power driver 64 a and the image driver 64b (collectively drivers 64). In some embodiments, the drivers 64 mayinclude multiple channels for independently driving multiple OLEDs 66with one driver 64.

The power driver 64 a may be connected to the OLEDs 66 by way of scanlines S₀, S₁, . . . S_(m-1), and S_(m) and driving lines D₀, D₁, . . .D_(m-1), and D_(m). OLEDs 66 receive on/off instructions through thescan lines S₀, S₁, . . . S_(m-1), and S_(m) and generate drivingcurrents corresponding to data voltages transmitted from the drivinglines D₀, D₁, . . . D_(m-1), and D_(m). The driving currents are appliedto each OLED 66 to emit light according to instructions from the imagedriver 64 b through driving lines M₀, M₁, . . . M_(n-1), and M_(n). Boththe power driver 64 a and the image driver 64 b transmit voltage signalsthrough respective driving lines to operate each OLED 66 at a statedetermined by the OLED controller 62. Each driver 64 may supply voltagesignals at a suitable duty cycle and/or amplitude sufficient o operateeach OLED 66.

Drivers 64 may include one or more integrated circuits that may bemounted on a printed circuit board and controlled by OLED controller 62.Drivers 64 may include a voltage source that provides a voltage to OLEDs66 for example, between the anode and cathode ends of each OLED layer.This voltage causes current to flow through the OLEDs 66 to emit light.Drivers 64 also may include voltage regulators. In some embodiments, thevoltage regulators of the drivers 64 may be switching regulators, suchas pulse width modulation (PWM) car amplitude modulation (AM)regulators. Drivers 64 using PWM adjust the driving strength by varyingthe duty cycle. For example, the OLED controller 62 may increase thefrequency of a voltage signal to increase the driving strength for anOLED 66. Drivers 64 using AM adjust the amplitude of the voltage signalto adjust the driving strength.

Each OLED 66 may emit light at an original brightness and original colorwhen driven with an original drive strength. When the drive strength isadjusted, like by PWM or AM, the light emitted from an OLED 66 will varyfrom the original brightness and original color. For example, the dutycycles for individual OLEDs 66 may be increased and/or decreased producea color or brightness that substantially matches a target color orbrightness for each OLED 66. Furthermore, over time and through use ofan OLED 66, the color and brightness of emitted light will also varyeven when driven with the original drive strength. In some embodiments,a controller 62 may adjust the drive strength of an OLED 66 throughoutits useful life such that the color and/or brightness of its emittedlight remains substantially the same, at least the same relative toother OLEDs 66 of the display 14.

OLED controller 62 may adjust the driving strength by changing the driveinstructions given to the drivers 64. Specifically, OLED controller 62may send control signals to drivers 64 to vary the voltage and/or theduty cycle applied to certain OLEDs 66. For example, OLED controller 62may vary the voltage applied by drivers 64 to an OLED 66 to control thebrightness and/or the chromaticity of that OLED 66. By increasing thevoltage applied to an OLED 66, the brightness of that OLED 66 increases.In contrast, decreasing the voltage applied to an OLED 66 decreases itsbrightness. In other embodiments, the ratio of the voltages applied to agroup of OLEDs 66 may be adjusted to substantially match the brightnessof other OLEDs 66 while maintaining a relatively constant color.

OLEDs 66 may be arranged in groups within the display to form pixels.Pixels may include groups of OLEDs 66 (e.g., three or four) emittingdifferent colors, particularly complementary colors such as red, cyan,green, magenta, blue, yellow, white, and combinations thereof. Theselight colors from each OLED 66 are mixed according to instructions fromthe OLED controller 62 to create specific colors, including white, foreach pixel. Together, the specific colors for each pixel of the display14 form an image on the display 14. The driving strength of some or allof the OLEDs 66 may be adjusted to achieve a uniform appearance for thedisplay 14. An ideal uniform display 14 may be such that if each pixelwas instructed to emit the same color and brightness, a user would notperceive color or brightness variations across the display 14. Rather,the entire display would have substantially the same color andbrightness as perceived by the user.

The age of each OLED 66 and the ambient environment may alter theappearance of a display or portions of it unless these effects arecompensated. OLEDs 66 of different colors typically do not have the sameaging profiles. Some colored OLEDs, like red OLEDs, may producesubstantially the same colored light at substantially the samebrightness for many hours, while other colored OLEDs, particularly blueOLEDs, may exhibit substantial changes in color and brightness over thesame period. Generalized brightness and chromaticity profiles may bestored in memory 28 to use for dynamically compensating OLEDs 66. Tocompensate for such changes, different colored OLEDs 66 in the samepixel may be driven differently over time to emit light at the targetbrightness and/or target color. In addition, pixels may contain multipleOLEDs 66 of the same color so that some be deactivated after usefullifetime while others are activated.

In some embodiments, photodetectors 55 adjacent to OLEDs 66 provide thecontroller 62 with information related to the aging characteristics ofOLEDs 66. Photodetectors 55 may be coupled to the OLED controller 62 byway of photodetector lines P₀, P₁, . . . P_(k). In some embodiments asshown in FIG. 7, each photodetector 55 may be disposed with an OLED 66in a 1:1 ratio. Each photodetector 55 measures the light emitted by itsrespective OLED 66 and transmits this measurement to the OLED controller62. Photodetectors 55 may measure the chromaticity (color) andbrightness of emitted light. The OLED controller 62 may determinecompensation adjustments to each OLED 66 based on a comparison betweenthe measured and target values for color and/or brightness of each OLED66.

Complementary colors of light may be combined to produce substantiallywhite light. However, different light sources may not produce the sameshade of white. A let white point of a light source is a set ofchromaticity values used to compare light sources. The white point of apixel is associated with its color and its component OLEDs. With respectto pixels of combined light sources, the required driving strength foreach component color to maintain a white point may change due tonumerous factors, including aging.

In some embodiments, compensate e for brightness and/or color shifts dueto aging of OLEDs, OLED controller 62 may increase the driving strengthof aged OLEDs 66, decrease the driving strength of less aged OLEDs 66 orincrease the driving strength of some aged OLEDs 66 and decrease thedriving strength of other less aged OLEDs 66. Based on measurements fromphotodetectors 55, OLED controller 62 may determine the direction of thewhite point shift of a pixel and increase the driving strength of one ormore OLEDs 66 within or near the pixel with a color complementary to thewhite point shift. For example, if a photodetector 55 has detected thatthe white point of pixel has shifted towards a blue tint, OLEDcontroller 62 may increase the driving strength of yellow tinted OLEDs66 in or near that pixel. OLED controller 62 also may decrease thedriving strength of one or more OLEDs 66 with a tint similar to thedirection of the detected white point shift in this pixel. For example,if the white point has shifted towards a blue tint in a particularpixel, the OLED controller 62 may decrease the driving strength of bluetinted OLEDs 66 in that pixel.

OLED controller 62 may govern operation of a driver 64 using informationstored in memory 28. For example, memory 28 may store values definingthe target brightness and/or color of each OLED 66, as well ascalibration curves, tables, algorithms, or the like. The memory 28 mayalso store values defining driving strength adjustments that may be madeto compensate for a shift in the emitted brightness or color. In someembodiments, the OLED controller 62 may dynamically adjust the drivingstrengths throughout operation of the display 14 to maintain a lightoutput that matches the target brightness or color. For example, OLEDcontroller 62 may receive transmitted information from photodetectors 55describing color and/or brightness of the emitted light. Using thetransmitted information from photodetectors 55, OLED controller 62 mayadjust the driving strengths to maintain a light output from each OLED66 that matches the target brightness and/or color for that OLED 66. Inan embodiment, OLEDs 66 may not be adjusted to compensate fordifferences between targeted and measured color and brightness if theadjustment would not be perceivable. An adjustment may not beperceivable if the difference between emitted and targeted light isslight.

In other embodiments, OLED controller 62 may receive signals from othersources instead of or in addition to, photodetectors 55. For example,OLED controller 62 may receive user transmitted information throughinput structure 16 (FIG. 2) of electronic device 10. Electronic device10 may include hardware and/or software components allowing useradjustment of the brightness and or color emitted by OLEDs 66 across thedisplay 14, or for particular portions of the display 14. In someembodiments, display 14 may include a brightness control that allows auser to select the brightness within a set range. In other embodiments,display 14 may include a color temperature control that allows a user toselect the color temperature (for example, from a set of fixed values)of the light emitted when display 14 receives an electrical signalcorresponding to a white light. OLED controller 62 also may receiveinput from the device 10. For example, the device 10 may include a clockthat tracks total operating hours of OLEDs 66. In some embodiments, OLEDcontroller 62 may compare the operating hours to a calibration curve ortable stored in memory 28 to determine a driving strength adjustment inconjunction with other adjustments made to OLEDs 66.

FIG. 8 depicts a flowchart of a method 100 for employing photodetectors55 to adjust the brightness and/or color of OLEDs 66 of a display 14 tocompensate for aging. Aging may include shifts in the chromaticity orluminance of an OLED 66 over time and use. The OLED aging method 100 maybegin by detecting (block 102) light emitted by the OLEDs 66. In someembodiments, each photodetector 55 and each OLED 66 are disposed in thedisplay in a 1:1 ratio. Other ratios are envisioned, including but notlimited to 1:2, 1:3 1:4, 1:6, 1:50, 1:100, 1:200 or ranges therebetween. An OLED controller 62 receives signals relating to the detectedlight from each photodetector 55. The OLED controller 62 then compares(block 104) the properties of light emitted from each OLED 66 to thetarget color and brightness values for each OLED 66. If a deviationexists, then the controller determines (node 106) whether compensationis needed for each OLED. Compensation may not be made if the adjustmentwould be imperceptible to end users or if the end user has disabled suchadjustments, etc. In such circumstances where compensation is not made,the OLED controller 62 continues to monitor the signal fromphotodetectors 55 to determine when adjustments would be desirable.

If compensation for an OLED 66 should be made, the OLED controller 62then determines (block 108) the compensation for each OLED 66 so thatthe emitted light substantially matches the targeted emitted light foreach respective OLED 66. The compensation may be determined byconsidering numerous factors, including OLED specific factors like themeasured emitted light properties, present drive strength, previousdrive strength adjustments, recorded operating hours, and/or informationstored in memory 28 like calibration curves, algorithms, and charts.Based on these factors, the OLED controller 62 may then determine thechanges in brightness and/or color needed to compensate each OLED 66 forthe aging detected by the proximate photodetector 55. Changes inbrightness and/or color for each OLED 66 may improve the image qualityof a display 14.

For example, an OLED 66 may have aged more rapidly due to defectivecomponents, use, temperature, or other factors. This differentially agedOLED 66 may affect the appearance or viewability of the display becausethis OLED 66 has a different brightness and/or color from other nearbyOLEDs 66 that aged normally. The OLED controller 62 may determine adriving strength adjustment to the differentially aged OLED 66 to makethe emitted light substantially match other OLEDs 66 or a color and/orbrightness target. Alternatively, the OLED controller 62 may determine adriving strength adjustment to the other less aged OLEDS 66 orsurrounding OLEDs 66 to make the differentially aged OLED 66 lessnoticeable than before. As another alternative, the OLED controller 62may determine driving strength adjustments to the differentially agedOLED 66 and the normally aged. OLEDs 66 to improve the overallviewability of the display. The OLED controller 62 may employ AM, PWM,or other suitable techniques to vary the driving strength.

As discussed above, aging compensation adjustments to the drivingstrength of OLEDs 66 may be based on different factors. Adjustments maybe made by the OLED controller 62 based on operating time and comparisonwith compensation information 70 stored in memory 28, the signal fromphotodetectors 55, and combinations thereof. For example, the OLEDcontroller 62 may drive the OLEDs 66 in each zone according tocalibration curves and algorithms stored in memory 28 and make finetuning adjustments based on the signal from each photodetector 55. Oncethe new driving strengths have been determined, OLED controller 62 maytransmit (block 110) the adjustment instructions to the drivers 64.

In some embodiments, each photodetector 55 may be disposed in thedisplay 14 with more than one OLED 66. In one embodiment illustrated inFIG. 9, photodetectors 55 are disposed in zones 60 of the display 14. Aphotodetector 55 may be disposed in the display 14 in each zone 60 todetect light incident to each zone 60. For example, light received byeach zone 60 across the display 14 may not be uniform, affecting theappearance of the display. As described above, photodetectors 55 maydetect light properties including the chromaticity and brightness. Thephotodetectors 55 may transmit information in the form of an electricalsignal in response to the detected light to the OLED controller 62.

In an embodiment, the display 14 includes an array of zones 60. Eachzone 60 includes at least one photodetector 55 and at two or more OLEDs66 proximate to the photodetector 55. In some embodiments, thephotodetectors 55 may be able to detect red, green, blue, and/or whitelight and the intensities of such light. Photodetectors 55 that detect acertain color of light may be used to adjust the driving strength ofproximate OLEDs 66 that emit that color of light. Furthermore, in someembodiments, zones 60 may overlap, such that some OLEDs 66 may lie inmore than one zone. For example, each zone 60 may include multiple OLEDs66 of only one OLED color (e.g., red zones, blue zones, and greenzones). In one embodiment, one portion of the display 14 may includemultiple overlapping zones where each zone 60 has a photodetector 55capable of recognizing a particular color. For example, a first array ofzones 60 may include a first OLED color (e.g., red) and a firstphotodetector 55 configured to detect the first OLED color, a secondarray of zones 60 overlapping the first array may include a second OLEDcolor (e.g., green) and a second photodetector 55 configured to detectthe second OLED color, and a third array of zones 60 overlapping boththe first and second arrays may include a third OLED color (e.g., blue)and a third photodetector 55 configured to detect the third OLED color.This may reduce the number of photodetectors 55 utilized while providinginformation on zones 60 of OLEDs 66 of a particular color forfine-tuning adjustments to the display 14.

The zones 60 may be arranged in a grid or in a matrix over the plane ofthe display 14 as shown in FIG. 9, but zone arrangements may not belimited to this configuration. In some embodiments, zones 60 may bearranged in strips, circles, or irregular shapes. Zones 60 may be ofuniform shape and size across the display 14, or have varied shapes andsizes. In some embodiments, certain areas of the display 14 will havemore zones 60 and thus more photodetectors 55 than others areas. Zones60 may be defined as having a certain number of OLEDs 66 or as the OLEDs66 closest to each photodetector 55. Furthermore, in some embodimentsphotodetectors 55 may be arranged only in corner zones 50 or edge zones52, or in other embodiments, only in interior zones 54.

FIG. 10 illustrates a schematic of an OLED array with photodetectorsdisposed in zones 60 of OLEDs 66, A display 14 may have an array ofOLEDs 66, photodetectors 55, a power driver 64 a, an image driver 64 b,a controller 62, and possibly other components. OLEDs 66 may be arrangedin zones 60 such that each zone 60 includes a photodetector 55. Asdescribed above, each zone 60 may contain one or more OLEDs 66. In anembodiment as shown in FIG. 10, each zone 60 may include a pixel groupcontaining one red OLED 66R, one green OLED 66G, one blue OLED 66B andone white OLED 66W. In other embodiments, each zone 60 may include adifferent number or color set of OLEDs 66, and each zone 60 may not belimited to the OLEDs 66 of a single pixel. The OLEDs 66 and drivers 64of the embodiment shown in FIG. 10 may operate in substantially the samemanner as described in FIG. 7. Similarly, the OLED controller 62 mayadjust the driving strength of each OLED 66 or zone 60 of OLEDs 66.

Photodetectors 55 are coupled to the OLED controller 62 by way ofphotodetector lines P₀, P₁, . . . P_(k). In some embodiments as shown inFIG. 10, each photodetector 55 may be disposed with a zone 60 of OLEDs66. Each photodetector 55 measures the light incident to or emitted byits respective zone 60. In some embodiments, the measured light is lightemitted by OLEDs 66 within the zone 60 and/or ambient light fromexternal sources. Photodetectors 55 may measure the color and/orbrightness of the received light. Each photodetector 55 may transmitsignals relating these measurements within the zone 60 to the OLEDcontroller 62.

Each OLED 66 emits light in response to the driving signals supplied bythe drivers 64. The color and brightness of the emitted light may dependat least in part on the supplied driving signals and the internalcomponents of the OLED 66. Other light sources may affect the quality ofthe light emitted by each OLED 66. For example, a bright light incidentto a display 14 may greatly diminish the readability of text or graphicsshown on the display 14 causing the display image to appear washed out.As another example, in dim light conditions, the OLED display 14 mayneed to emit light at a reduced brightness for a display image to bereadable. Operating an OLED display 14 at a high brightness level at alltimes may not be desirable for many reasons including, powerconsumption, eye strain, and aging effects on the OLEDs 66.

Other situations may exist where an OLED display 14 is to be used indifferent colors of ambient light. The color of the ambient light mayaffect the perceived color of the display 14. For example, a whitedisplay image may appear yellow when used in an environment with ayellow tinted ambient light.

Photodetectors 55 disposed throughout the display 14 in zones 60 maydetect light incident to each zone 60 of the display 14. Photodetectors55 may transmit signals relating to the detected light to OLEDcontroller 62 to determine how to counter the effects of the ambientlight on the perceived brightness and color of the display 14. Theperceivability of a display may depend on the relationship between theproperties of light incident on each zone 60 and the emitted brightnessand color of each zone 60. For any ambient light conditions, an optimalperceivability setting may exist such that the perceived brightness andcolor of a zone 60 driven at that setting substantially matches thetarget brightness and color for that zone 60. The OLED controller 62 maydetermine the perceivability setting of a zone 60 based on the measuredlight values and target values for color and brightness of each zone.The OLED controller 62 may adjust the driving strengths of each zone 60of OLEDs 66 based on the perceived brightness and color of each zone tomatch an optimal perceivability setting for the zone 60. In anembodiment, driving each zone 60 at its optimal perceivability settingwould result in a uniform display appearance.

To optimize the perceivability of each zone 60 for the effects ofambient light, OLED controller 62 may increase the driving strength ofaffected zones 60 of OLEDs 66, decrease the driving strength of affectedzones 60 of OLEDs 66, or increase the driving strength of some affectedzones 60 of OLEDs 66 and decrease the driving strength of other lessaffected zones 60 of OLEDs 66. In some embodiments, the driving strengthof each zone 60 may be adjusted according to the ambient light detectedin each respective zone 60 to obtain an optimal perceivability settingfor each zone 60 of the display 14. For example, zones in a first potionof the display may be in a shadow, zones in a second portion of thedisplay may be in bright light, and zones in a third portion of thedisplay may be in a typical level of ambient light. Based on thedetected levels of ambient light for each zone, the OLED controller 62may decrease the driving strength of the zones in the first portion,increase the driving strength of the zones in the second portion, andnot adjust the driving strength of the zones in the third portion.

OLED controller 62 may govern operation of the driver 64 usinginformation stored in memory 28. For example, memory 28 may store valuesdefining the target brightness and/or color of each OLED 66, as well ascalibration curves, tables, algorithms, or the like. The memory 28 mayalso store values defining driving strength adjustments that may be madeto compensate for differences in the perceived brightness or targetcolor. In some embodiments, the OLED controller 62 may dynamicallyadjust the driving strengths of each zone 60 throughout operation of thedisplay 14 to maintain a uniform display appearance through matching theperceived brightness and color of each zone to the target brightness andcolor for each zone. In sonic embodiments. OLEDs 66 may not be adjustedto compensate for differences between targeted and perceived color andbrightness if the adjustment would not be perceivable.

FIG. 11 depicts a flowchart of a method 74 for employing photodetectorsto adjust OLEDs 66 or zones 60 of a display to compensate fordifferences in targeted and perceived brightness and/or color of emittedlight. The perception of emitted light from a display may depend onambient light incident to the display 14. The ambient light compensationmethod 76 may begin by detecting (block 76) light incident to thedisplay 14. In some embodiments, each photodetector 55 is disposed withan OLED 66 as described above. In other embodiments, each photodetector55 is disposed in the display 14 with a group of OLEDs 66 in a zone 60.A controller 62 receives signals related to the detected light acrossthe display 14 from each photodetector 55. The controller 62 thendetermines (block 78) the perceived properties of the light emitted fromeach zone 60 based on the detected light. The controller 62 thendetermines (node 80 whether compensation is desirable for each OLED 66or zone 60. This determination may be based on whether a differencebetween the perceived and targeted color and brightness values for eachzone 60 exists. Compensation may not be desirable if the adjustmentrequired would be imperceptible to end users or if the end user hasdisabled such adjustments. etc. In such circumstances where compensationis not desirable, the OLED controller 62 continues to monitor the signalfrom photodetectors 55 to determine when adjustments would be desirablefor each zone 60.

If compensation for an OLED 66 or zone 60 is desired, the OLEDcontroller 62 then determines (block 82) the compensation for each OLED66 so that the perceived emitted light substantially matches thetargeted light for each OLED 66 or zone 60. The compensation may bedetermined by considering numerous factors, including OLED specificfactors like the measured emitted light properties present drivestrength, previous adjustments, recorded operating hours, and/orinformation stored in memory 28 like calibration curves, algorithms, andcharts. Changes in brightness and/or color for each OLED 66 or zone 60may improve the image quality of a display. The determined compensationmay be in the form of adjustments to the driving instructions of eachOLED 66 or zone 60,

In some embodiments, the OLED controller 62 may determine a separatedriving strength adjustment for each zone 60 based on the determinedperceived light characteristics due to ambient light on each zone 60 toobtain an optimal perceivability setting for each zone. In otherembodiments, the OLED controller 62 may determine a driving strengthadjustment for each zone 60 based on the perceived light emitted fromadjacent zones 60. For example, the OLED controller 62 may increase thebrightness of zones 60 in bright light to substantially match theperceived brightness of adjacent zones 60 in dim light. Alternatively,the OLED controller 62 May decrease the brightness of zones 60 in dimlight to substantially match the perceived brightness of zones 60 inbright light. In other embodiments, the OLED controller 62 may determinedriving strength adjustments for each zone 60 to obtain an optimalperceivability setting for the entire display 14. The OLED controller 62may employ AM. PWM, or other suitable techniques to vary the drivingstrength.

As discussed above, compensation adjustments to the driving strength ofOLEDs 66 in each zone 60 based on detected ambient light may be based ondifferent factors. Adjustments may be made by the ( )ED controller 62based on operating time and comparison with compensation information 70stored in memory 28, the signal from photodetectors 55, and combinationsthereof. For example, the OLED controller 62 may drive the OLEDs 66 ineach zone according to calibration curves and algorithms stored inmemory 28 and may make fine tuning adjustments based on a signal fromeach photodetector 55. Once the new driving strengths have beendetermined, OLED controller 62 may transmit (block 86) the adjustmentinstructions to the drivers 64.

In some embodiments, photodetectors 55 may be utilized as proximitysensors. Photodetectors 55 utilized as proximity sensors may includephotodiodes and photocells. Proximity sensors may detect nearby objectsthrough observing changes in an ambient electromagnetic field or signal(e.g., infrared or visible light). Alternatively, proximity sensors maydetect changes in an emitted electromagnetic field or signal.

Photodetectors 55 disposed in the display 14 to be utilized as proximitysensors may be disposed with each OLED 66 as shown in FIG. 7, disposedwith zones 60 of OLEDs 66 as shown in FIG. 10, or disposed on theperiphery of the display 14 as shown in FIG. 12. As described above,each photodetector 55 is coupled to the OLED controller 62. When aphotodetector 55 senses a nearby object, the photodetector 55 maytransmit information in the form of an electrical signal to the OLEDcontroller 62.

Photodetectors 55 disposed in the display 14 and utilized as proximitysensors may provide a number of functionalities to an electronic device10. In some embodiments, photodetectors 55 may be used to turn a display14 or portion of a display 14 on or off in a variety of situations,including when a laptop display is closed, a cellular phone is placed byan ear, a handheld device is placed in a pocket or a portion of adisplay is covered. For example, if a portion of the display 14 iscovered and fully obscured from view, the OLED controller 62 maydetermine that the OLEDs 66 in the covered zones should be turned offand only the OLEDs 66 in unobscured zones of the display should remainon. The unobscured zones of the display may show a shrunken version ofthe original display image or a modified image suitable for the smallerunobscured area.

In another embodiment, proximity sensors incorporated in a display mayadd touch screen functionality. For example, multiple photodetectors 55may be utilized to predict the location at which an approaching object(e.g., a finger) may touch the display. In an embodiment, multiplephotodetectors 55 may be used to discern approaching objects such thatan entire cell phone display 14 is turned off when placed next to auser's ear, but the display 14 remains turned on when touched by auser's finger.

FIG. 13 depicts a flowchart of a method 88 for employing photodetectorsas proximity sensors and making appropriate alterations to the displaybased on sensed nearby objects. The method 88 may begin by detecting(block 90) objects near each zone. Each photodetector 55 to be utilizedas proximity sensors may be disposed with each OLED 66, zones 60 ofOLEDs 66, or larger portions of the display 14. Each photodetector 55 isalso coupled to an OLED controller 62. Photodetectors 55 may transmitinformation corresponding to detected nearby objects to the OLEDcontroller 62. The transmitted information may be in the form ofelectrical signals representing changes in the amount of light receivedby a photodetector 55 or distance from the photodetector 55 to theobject that OLED controller 62.

Based on the signals transmitted by each photodetector 55, the OLEDcontroller 62 determines (node 92) whether all or portions of thedisplay 14 need to be adjusted. This determination may be based on manyfactors, including the distance to the detected object and to the size,direction, and identity of the detected object. For example, a fingerapproaching the display 14 may require an adjustment to at least aportion of the display due to the finger's distance and identity;however, a hand passing over the display 14 may not require anadjustment due to the hand's distance and direction. As another example,the controller may determine the difference in transmitted photodetectorsignals between operating the display 14 in a dark room and placing thedisplay 14 into a pocket so that the display remains on in a dark roombut turns off in a pocket. In such circumstances where adjustment is notneeded, the OLED controller 62 continues to monitor the signal fromphotodetectors 55 to determine when adjustments would be needed to partsof the display 14.

If adjustment for all or part of the display 14 is needed, the OLEDcontroller 62 then determines (block 94) the adjustment needed for eachOLED 66 of the display 14. The adjustment needed may be determined byconsidering numerous factors, including current use of the electronicdevice 10, ambient light, what portions of the display detect theobject(s), and information stored in memory 28. The determinedcompensation may be in the form of adjustments to the driving signal orscan signal of each OLED 66 or zone 60. Once the new driving strengthshave been determined, OLED controller 62 may transmit (block 98) theadjustment instructions to the drivers 64.

While many of the embodiments illustrated and described mention photodetectors disposed with OLEDs or zones of OLEDs, it should be furtherunderstood that photodetectors disposed in the display with any numberof OLEDs may be utilized in any method herein described. Furthermore, itis intended that the photodetectors may be used for aging compensation,ambient light compensation, proximity sensing, and combinations thereofas illustrated in FIGS. 8, 11, and 13.

The specific embodiments described above have been shown by way ofexample, and it should be understood that these embodiments may besusceptible to various modifications and alternative forms. It should befurther understood that the claims are not intended to be limited to theparticular forms disclosed, but rather to cover all modifications,equivalents, and alternatives falling within the spirit and scope ofthis disclosure.

What is claimed is:
 1. A display, comprising: an array of pixelsincluding at least a first pixel in a first region of the display and asecond pixel in a second region of the display; a plurality ofphotodetectors that detect ambient light including at least a firstphotodetector in the first region of the display and a secondphotodetector in the second region of the display, wherein the firstphotodetector generates a first ambient light signal in response toambient light incident on the first region of the display and the secondphotodetector generates a second ambient light signal in response toambient light incident on the second region of the display; and acontroller that determines control signals for the pixels to compensatefor differences in ambient light across the display, wherein the controlsignals include at least a first control signal that provides a firstcompensation to the first pixel based on the first ambient light signaland a second control signal that provides a second compensation to thesecond pixel based on the second ambient light signal, wherein the firstcompensation is different than the second compensation.
 2. The displaydefined in claim 1 wherein the pixels comprise organic light-emittingdiode pixels.
 3. The display defined in claim 1 wherein the first andsecond photodetectors are disposed at the periphery of the array ofpixels.
 4. The display defined in claim 1 wherein the first and secondphotodetectors are each disposed between a respective pair of pixels inthe array of pixels.
 5. The display defined in claim 1 wherein eachphotodetector in the plurality of photodetectors is disposed in arespective zone in the display and wherein each zone contains arespective group of pixels in the array of pixels.
 6. The displaydefined in claim 5 wherein the controller determines control signals forthe group of pixels in a given zone based on ambient light signals fromthe photodetector in the given zone.
 7. The display defined in claim 1wherein at least some of the photodetectors are color-sensitive.
 8. Thedisplay defined in claim 1 wherein the control signals compensate fordifferences in ambient light across the display by adjusting pixelbrightness.
 9. The display defined in claim 1 wherein the controlsignals compensate for differences in ambient light across the displayby adjusting pixel color.
 10. A display, comprising: an array of pixels;a plurality of photodetectors that generate signals in response todetected light, wherein each photodetector is interposed between arespective pair of pixels in the array; and a controller that controlsthe operation of the pixels based at least in part on the signalsgenerated by the photodetectors.
 11. The display defined in claim 10wherein the pixels comprise organic-light emitting diode pixels andwherein the photodetectors generate the signals at least partly inresponse to light emitted from the organic-light emitting diode pixels.12. The display defined in claim 11 wherein the controller determinescontrol signals for the pixels based at least in part on the signalsfrom the photodetectors to compensate for color differences across thedisplay, wherein a first group of pixels in the array is compensateddifferently than a second group of pixels in the array.
 13. The displaydefined in claim 10 further comprising: control lines that transmitcontrol signals from the controller to the pixels; and signal lines thattransmit the signals from the photodetectors to the controller.
 14. Thedisplay defined in claim 13 wherein at least some of the signal linesare interspersed among the control lines.
 15. The display defined inclaim 10 wherein the photodetectors generate the signals at least partlyin response to ambient light.
 16. The display defined in claim 15wherein the controller determines control signals for the pixels basedat least in part on the signals from the photodetectors to compensatefor differences in ambient light conditions across the display; whereina first group of pixels in the array is compensated differently than asecond group of pixels in the array.
 17. A display, comprising: an arrayof pixels including at least first and second pixels; a proximity sensorcomprising at least one photodetector that is interposed between thefirst and second pixels, wherein the proximity sensor generates signalsin response to external objects in proximity to the display; and acontroller that controls the array of pixels based at least partly onthe signals generated by the proximity sensor.
 18. The display definedin claim 17 further comprising an additional proximity sensor thatgenerates signals in response to external objects in proximity to thedisplay, wherein the additional proximity sensor comprises at least onephotodetector that is interposed between third and fourth pixels in thearray.
 19. The display defined in claim 18 wherein the controllerdetermines control signals for the first and second pixels based atleast partly on the signals generated by the proximity sensor and forthe third and fourth pixels based at least partly on the signalsgenerated by the additional proximity sensor.
 20. The display defined inclaim 19 wherein the first and second pixels are located in a firstregion of the display, wherein the third and fourth pixels are locatedin a second region of the display, wherein the controller turns off thefirst and second pixels and leaves on the third and fourth pixels whenthe signals from the proximity sensor and the additional proximitysensor indicate that the first region of the display is covered and thesecond region of the display is uncovered.